Amazon.com: IIVVERR 2 Pieces Green Iron Toroid Ferrite Core 1.2in x 0.7in x 0.5in (2 Pieces Green Iron Toroid Ferrite Core 1.2in x 0.7in x 0.5in : Industrial & Scientific
PATIKIL Ferrite Toroid Core 22.5mm x 13.8mm x 10mm, 10 Pack Transformer Inductor Coil Ring, Black: Amazon.com: Industrial & Scientific
uxcell 10 Piece Inductor Coils Green Ferrite Cores 10 mm x 6 mm x 5 mm: Amazon.com: Industrial & Scientific
AEcreative T200-2 ferrite Iron Powder core toroid for Amateur ham HF Band balun UNUN Tuner Type 2 red 1.5KW : Amazon.ca: Electronics